Electric drive unit

ABSTRACT

The invention relates to an electric drive unit comprising an electronic control module and an electric motor. The cooling of the components of the electric drive unit should be effected in a simple manner. To this end, the hub of the impeller wheel, which is situated on the rotation axis of the electric motor and provided for producing a working air flow, has a two-walled design, whereby a hub inner space is formed between the outer wall and the inner wall of the hub of the impeller wheel. At least one cooling surface of the cooling body, said surface being in contact with components of the electronic control module, projects into the hub inner space. A gap communicating with the hub inner space, is formed between the hub of the impeller wheel and a carrier section which supports the electronic control module and the electric motor. In addition, through-holes communicating with the hub inner space are provided in at least one component of the electric drive unit. When the electric drive unit operates and the impeller wheel is in motion an air flow between the gap and the through-holes is established. The invention also relates to an electric drive unit with a fan motor.

The invention relates to an electric drive unit according to the preamble of patent claim 1 as known from German Patent Publication DE 41 22 529 A1.

Electrical drive units are used in a multitude of application areas, for example in home appliances or in the area of motor vehicles. Particularly in motor vehicles, different movable components of the motor vehicle can be adjusted by means of electrical drive units, for example seats, window lifters, sun roofs, etc., or components may be operated with a variable r.p.m. (for example fans). Electrical drive units used for ventilation comprise an electric motor (fan motor) functioning as a drive device for providing electrical drive power, an electronic control module for controlling the electric motor, for example for the r.p.m. and power regulation (closed loop control) of the electric motor and a rotatable impeller wheel driven by the electric motor as a work performing mechanism for producing a working airflow.

The electronic control module comprises structural components which, as a rule, are mounted on a printed circuit board. These structural components include particularly also power components with a high dissipation power because in the operation of the electric drive unit frequently currents flow with a very high amperage, for example 50 A. Accordingly, a high input power of the electrical drive unit and thus of the power components results. Therefore, a sufficient cooling for the electronic control module, particularly for the structural components of the electronic control module, must be provided especially for the dissipation of the power loss of the structural power components. For this purpose the structural components of the electronic control module or at least the power components thereof, are brought into contact with cooling surfaces of a cooling body. More specifically, the power components are mounted on these cooling surfaces of the cooling body.

In order to assure a compact construction and thus a small structural size of the electric drive unit, it is necessary on the one hand to build the electronic control module and the electric motor mounted on a motor carrier as small as possible while on the other hand positioning the electronic control module as close as possible to the electric motor. Particularly, the electronic control module should be directly connected to the motor carrier. In this case achieving a sufficient cooling of the structural components of the electronic control module poses a problem, particularly the dissipation of the power loss of the structural power components because the possibilities of cooling these components are substantially limited or even not available at all. In the German Patent Publication DE 41 22 529 A1 according to the preamble, the surface of the motor carrier functioning as a cooling body is increased by forming a ring wall for the motor carrier which extends into the area of the rotor of the electric motor, whereby the heat dissipation is improved without any increase in the space requirement for the electric drive unit.

It is the object of the invention to provide an electric drive unit according to the preamble of patent claim 1 in which a simple, reliable and cost effective construction and operation are made possible. This object is achieved according to the invention by the features in the characterizing clause of patent claim 1. Advantageous embodiments of the invention are provided by the further patent claims.

In the present electric drive unit the cooling of the structural components of the electronic control module, particularly of the power components of the electronic control module is realized by a cooling body having at least one cooling surface in contact with the structural components to be cooled. The present drive unit comprises an impeller wheel set on the rotational axis of the electric motor provided as a drive device. The impeller wheel acts as a work unit for producing a working air stream. In the present unit at least one cooling surface, preferably all cooling surfaces are at least partially, preferably completely, reaching into the hub of the impeller wheel. Stated differently at least one cooling surface extends at least partially into the hub of the impeller wheel. For this purpose the impeller wheel is constructed with a double wall including an outer wall and an inner wall and a hub inner space formed between the outer wall and the inner wall. The cooling surfaces of the cooling body are extended into the hub inner space of the impeller wheel. Hub chambers are formed in the hub inner space between the outer wall and the inner wall by radially extending ribs (lands) which cause a stiffening of the hub of the impeller wheel. The cooling surfaces of the cooling body that reach into the hub of the impeller wheel are introduced into the hub inner space up to the vicinity of these ribs, preferably directly bordering on these ribs. When the impeller wheel is set on the rotational axis of the electric motor, a gap is formed between the hub of the impeller wheel and a carrier section. The carrier section serves for supporting the electric motor and the electronic control module as well as for the securing of the electric drive unit. For example, the gap is formed between the outer wall of the hub of the impeller wheel and a casing forming a central part of the carrier section. Further, through-holes are formed at a suitable location of the electric drive unit for the air present in the hub inner space. Preferably the through-holes are formed in the hub of the impeller wheel, particularly as bores on the upper side of the hub of the impeller wheel and/or in the rotor of the electric motor. The through-holes are formed particularly as longitudinal holes on the top side of the rotor and/or on the bottom side of the carrier section, particularly on the underside of the casing functioning as a central part of the carrier portion. During the operation of the electric drive unit and due to the rotation of the impeller wheel, a working air flow is produced by the rotation of the wings of the impeller wheel secured to the outer wall of the hub of the impeller wheel. Due to this working air flow an air stream is also produced in this gap between the hub of the impeller wheel and the carrier section. The air stream causes a pressure differential between the air present in the area of this gap and the air present in the area of the through-holes. Stated differently, an imposed convection is generated by the active onflow at the gap for the air present in the hub inner space. Due to this imposed convection the heated air present in the hub inner space escapes through the respective exit hole either out of the gap or out of the through-holes, whereby cooling air is introduced into the hub inner space through entrance holes, either through the through-holes or through the gap, from the space outside, that is from outside of the hub of the impeller wheel. Thereby, the cooling surfaces of the cooling body present in the hub inner space are actively cooled with the air introduced from the space outside of the hub as a cooling medium flowing around the cooling surfaces which are correspondingly cooled.

Electric motors for use in the electric drive unit may be differently operated and configured fan motors. In this context asynchronous AC-motors which run asynchronously relative to the supply frequency, or synchronous motors which run in synchronism with the supplied frequency, may be used. These AC-motors are externally commutated. DC-motors maybe used which are self-commutating in dependency on the applied input voltage. Particularly brushless DC-motors operating as permanently excited synchronous motors may be used. In such motors the commutation is linked with a position recognition. Thus, these brushless DC-motors are operated as electronically commutated, self-commutating DC-motors (EC-DC-motors). More specifically, the self-commutation takes place depending on the input voltage applied to the individual coils. Further, different arrangements of the fixed stator relative to the rotating rotor may be selected. Particularly, in the so-called external rotor motors the rotor rotates on the outside of the stator and in so-called internal rotor motors the rotor rotates on the inside of the stator.

Advantageously, the present electric drive unit realizes a compact construction without any interference of the cooling surfaces of the cooling body provided for cooling, with the motion of the impeller wheel. This is so because the cooling surfaces are not positioned in the working air flow or they do not adversely influence the working air flow, whereby annoying noise that would otherwise result, do not arise. By utilizing the air flow that occurs when the electric drive unit operates, particularly of the active onflow at the gap between the hub of the impeller wheel and the carrier section, and the use of the pressure relationships caused thereby with the imposed convection of air out of the hub inner space, no separate cooling medium is required for cooling the cooling surfaces of the cooling body inside the hub inner space of the impeller wheel. The supply of external air for cooling into the inner space of the hub and the removal of heated air out of the hub inner space is accomplished by simple entrance holes and exit openings which possibly are already there. These holes are so constructed that a sufficient inflow of external air and thus the cooling of the cooling surfaces of the cooling body is assured. The pressure differential between the gap on the one hand and the through-holes on the other hand, the imposed convection in the hub inner space and the cooling effect are all independent of the flow direction of the working air flow produced by the motion of the impeller wheel. As a result, a good cooling effect is achieved independently of the installation direction of the impeller wheel and thus independently of the motion of the impeller wheel relative to the flow direction of the working air flow. The gap is formed between the hub of the impeller wheel and the carrier portion. The cooling effect depends on the removal of heated air from the hub inner space and on the supply of cool air from the external space. Thus, a multitude of wide ranging applications and use possibilities are achieved for the electric drive unit.

The electric drive unit will be described more closely in the following with reference to an example embodiment and in connection with the drawing, wherein:

FIG. 1 shows a three-dimensional illustration of the electric drive unit with the components separated from one another;

FIG. 2 is a plan view onto the bottom of the interconnected components of the electric drive unit;

FIG. 3 is a sectional view of the interconnected components of the electric drive unit;

FIG. 4 is a side view of the interconnected components of the electric drive unit; and

FIG. 5 is a sectional view of the interconnected components of the electrical drive unit showing a modified configuration of the components as compared to FIG. 3.

The electric drive unit 1 comprises, for example a brushless DC-motor 3 constructed as a fan motor of a motor vehicle. The motor functions as a drive device. The unit further includes an electronic control module 2 for controlling of the fan motor 3 particularly for varying the r.p.m. of the fan motor 3, an impeller wheel 4 for producing a working air flow (useful air flow) functioning as a working device and a carrier section 5 for mounting the electronic control module 2 and the fan motor 3.

The r.p.m. of the fan motor 3 shall, for example be variable within the r.p.m. range between 400 r.p.m. and 2400 r.p.m. (rated r.p.m.). The r.p.m. change is achieved by varying a DC-voltage supplied to the fan motor 3. The fan motor 3 delivers its defined power at the rated r.p.m. of, for example 2400 r.p.m. The fan motor 3 has, for example a maximum input power of 600 W with a motor input voltage of 12 V, whereby the maximum motor current is 50 A. This current is distributed onto the coil windings of the fan motor 3 by commutation (commutation of the motor sections of the fan motor 3).

The components of the fan motor 3 separated from one another are shown in FIG. 3, including the electronic control module 2, the impeller wheel 4, and the carrier section 5 of the electric drive unit 1. The structural components 21 of the electronic control module 2 which is arranged on the underside 332 of the motor carrier 33 are secured on a printed circuit board 22 (compare FIG. 3). Structural components 21 are particularly provided as commutation transistors for commutating the motor sections of the fan motor 3. For example, four commutation transistors constructed as field effect transistors are provided having connector pins in contact with contact points on the printed circuit board 22 or with a stamped grid 24. The housings of the field effect transistors are, for example arranged on cooling surfaces 71, for example made of aluminum, of the cooling body 7. In order to protect the structural components 21 of the electronic control module 2 the printed circuit board 22 is mounted in a housing 23, for example made of synthetic material. The stamped grid 24 is provided for the electrical connection of the structural components 21 and for providing an external connector possibility. The stamped grid 24 is formed of a plurality of stamped grid connector tabs 26 enclosed by synthetic material 25 by spraying. The stamped grid connector tabs 26 leading outside are integrated in at least one plug-in connector 27. Particularly at least one connector plug can be connected to the plug-in connector 27 for connecting the electric drive unit 1 with further structural packages, for example for connecting the electric drive unit 1 with the onboard power supply net of the motor vehicle for a voltage supply and/or with a switching unit for feeding a control signal for switching on the fan motor 3. Furthermore, the stamped grid 24 forms connector elements 28 which lead perpendicularly away from the plane of the printed circuit board 22. For example, six such connector elements 28 are provided, whereby for example two connector elements 28 are provided for the voltage supply of the fan motor 3 and four connector elements 28 are provided for the commutation of the fan motor 3. The connector elements 28 are made, for example of electrolytic copper with a thickness of, for example 0.8 mm and comprise, for example a square diameter of, for example 6 mm. The length of the connector elements 28 is selected in accordance with the height of the stator 31 of the fan motor 3 and thus depending on the power of the electric drive unit 1. The length of the connector elements 28 is, for example, about 70 mm.

The fan motor 3, for example constructed as an external rotor motor comprises a circular stator 31 formed of a plurality of stator coils 35 with coil windings 351. The stator 31 is mounted on the top side 331 of the motor carrier 33. The fan motor 3 further comprises a rotor 32 rotating about the stator 31 on the outside of the stator. The stator coils 35 are formed as circular segments and are arranged in such a way that a hole 38 is formed in the center in which the rotational axis 39 of the fan motor 3 is inserted. A plurality of holes, for example in the form of longitudinal holes, are formed in the top side 323 of the rotor 32. These longitudinal holes 322 are, for example arranged in a star shape around the rotational axis 39 of the fan motor 3. The motor carrier 33 comprises lead-throughs 34 (compare FIG. 3) for the connector elements 28 extending from the stamped grid 24 of the electronic control module 2. The connector elements 28 are led through the lead-throughs 34 to the individual stator coils 35. Contact elements in the form of contact hooks 36 and/or contact surfaces 37 are attached to the ends of the coil winding 351 of the stator coil 35 for realizing the connector contacts for the stator 3 or rather the stator coils 35. The contact elements 28 led through the lead-throughs 34 and along the inside of the hole 38 are electrically connected in a suitable manner, either with the contact hooks 36 or with the contact surfaces 37. For example, the connector elements 28 are welded to the contact surfaces 37. The holes 333 formed in the motor carrier 33 serve for securing the motor carrier 33 and thus the electric motor 3 and the electronic control module 2 to the carrier section 5.

The impeller wheel 4 comprises the hub 41 attached to the rotor 32 of the fan motor 3 and the wings 42 radially arranged on the outer wall 411 of the hub 41. For example seven wings 42 are provided. Through-holes, for example in the form of bores 43 are formed on the top side 412 of the hub 41. The bores 43 serve just as the longitudinal holes 322 on the top side 323 of the rotor 34 for the supply of cooling external air into the hub inner space 414 formed between the outer wall 411 and the inner wall 413 of the hub 41 or they serve for the discharge of the air present in the hub inner space 414. The impeller wheel 4 is set on the carrier section 5 on the under side 415 of the hub 41.

The carrier section 5 comprises a central portion 51, for example shaped as a casing in the form of a circular ring. A plurality of radially arranged lands 52 are provided on the outer wall 511 of the central portion 51 for securing the carrier section 5 and thus the electrical drive unit 1. The inner space 54 of the central portion 51 is provided for the installation of the electronic control module 2, whereby a plurality of chambers 53 are formed on the inner wall 512 of the central portion 51 for receiving the cooling surfaces 71 of the cooling body 7 of the electronic control module 2. Furthermore, a plurality of retainer openings 55 are provided on the inner wall 512 of the central portion 51 neighboring to the chambers 53 and corresponding to the holes 333 in the motor carrier 33. The motor carrier 33 and thus the fan motor 3 are secured through these retainer openings 55 from the top side 513 of the carrier section 5 by means of suitable securing means for example by means of screws in the central portion 51 of the carrier section 5. The carrier section 5 in turn is secured by means of the lands 52 to the installation location provided for and suitable for the installation on the chassis or aggregates of the motor vehicle, for example screwed to the radiator of the motor vehicle. In FIG. 2 is shown a bottom view of the assembled electrical drive unit 1. As is visible from this, the hub 41 of the impeller wheel 4 is constructed with a double wall including the outer wall 411 and the inner wall 413. The hub inner space 414 formed between the outer wall 411 and the inner wall 413 is subdivided in a partial area into hub chambers 45 by ribs 44. The ribs 44 are arranged between the outer wall 411 and the inner wall 413 of the hub 41 and cause a stiffening of the hub 41 of the impeller wheel 4. The wings 42 are secured to the outer wall 411 of the hub 41 of the impeller wheel 4. The inner wall 413 of the hub 41 of the impeller wheel 4 is connected to the rotor 32 of the electric motor 3, said rotor rotating about the stator 31. The cooling surface 71 of the cooling body 7 of the electronic control module 2 are inserted into the hub inner space 414, preferably to such an extent that they border directly on the hub chambers 45 formed in the hub inner space and thus on the ribs 44.

A sectional view of the assembled electric drive unit is shown in FIG. 3 and FIG. 4 shows a side view thereof. The rotational axis 39 of the rotor 32 of the fan motor 3 rotating about the stator 31 is inserted into the hole 38 and secured in position by bearings. The magnets 321 of the rotor 32 are for example secured to the inside of the rotor 32. The electronic control module 2 which is arranged below the motor carrier 33, is positionable completely within the dimensions of the stator 31, more specifically the control module 2 does not extend at any point beyond the motor carrier 33. This is possible due to the central arrangement of the electronic control module 2 and particularly due to the electrical connection of the electronic control module 2 and the fan motor 3 through the connector elements 28 that are centrally led in the electric drive unit 1.

A gap 6 is formed between the top side 513 of the central portion 51 of the carrier section 5 and the underside 415 of the hub 41 of the impeller wheel 4. The gap communicates with the inner hub space 414. A pressure differential arises between the air present in the area of the gap 6 and the air present in the area of the bores 43 and the longitudinal holes 322. This pressure differential is independent of the flow direction of the working air flow produced by the motion of the wings 42 of the impeller wheel 4. As a result, a convection of the air between the gap 6 on the one hand and the bores 43 and the longitudinal holes 322 on the other hand occurs through the inner hub space 414, whereby the air which has been heated due to the contact with the cooling surfaces 71 of the cooling body 7, discharges from the inner hub space 414 and cool outer air from the surrounding space is supplied into the hub inner space 414. Hereby, and as a result, a cooling of the cooling surfaces 71 of the cooling body 7 and thus a cooling of the structural components 21 of the electronic control module 2 arranged on these cooling surfaces 71, is caused. The cooling surfaces 71 extend into the hub inner space 414 preferably directly to the hub chambers 45, i.e. they border directly on the hub chambers 45.

According to the sectional drawing of FIG. 5 showing another example embodiment of the electric drive unit 1, the cooling surfaces 71 of the cooling body 7 are connected with the motor carrier 33. Particularly, the cooling surfaces 71 of the cooling body 7 are arranged as a portion of the motor carrier 33 in the rim area of the motor carrier 33, i.e. the motor carrier 33 and the cooling surfaces 71 are constructed as an integral unit. The structural components 21 of the electronic control module 2 which are to be cooled are arranged on the underside of the cooling surfaces 71. As a result, the cooling surfaces 71 inside the hub inner space 414 are cooled, whereby the structural components 21 of the electronic control module 2 to be cooled, are also cooled. 

1. An electric drive unit with the following components: an electric motor (3) arranged on the top side (331) of a motor carrier (33) and including a stator (31) and a rotor (32), said rotor rotating around a rotational axis (39) relative to the stator (31), an electronic control module (2) for controlling the electric motor (3), arranged on the bottom side (332) of the motor carrier (33) and including structural components (21), a cooling body (7) having at least one cooling surface (71) in contact with the structural components (21), a carrier section (5) for supporting the electronic control module (2) and the electric motor (3), and an impeller wheel (4) set on the rotational axis (39) of the electric motor (3) for producing a working air flow, characterized in that the hub (41) of the impeller wheel (4) is constructed with a double wall including an inner wall (413) and an outer wall (411), and a hub inner space (414) formed between the outer wall (411) and the inner wall (413), that at least one cooling surface (71) of the cooling body (7) reaches at least partially into the hub inner space (414), and that the hub inner space communicates with a gap (6) and with through-holes (322, 43), said gap (6) being formed between the hub (41) of the impeller wheel (4) and the carrier section (5), said through-holes being formed in at least one component of the electrical drive unit (8), whereby an air flow is formed between the gap (6) and the through-holes (322, 43) when the electric drive unit operates and the impeller wheel (4) moves.
 2. The electric drive unit of claim 1, characterized in that the through-holes (43) are provided in the hub (41) of the impeller wheel (4).
 3. The electric drive unit of claim 2, characterized in that the through-holes (322) are formed as bores in the top side (412) of the hub (41) of the impeller wheel (4). 4-16. (canceled)
 17. The electric drive unit of claim 1, characterized in that the through-holes (322) are provided in the rotor (32) of the electric motor (3).
 18. The electric drive unit of claim 17, characterized in that the through-holes (322) are formed as elongated holes in the top side (323) of the rotor (32).
 19. The electric drive unit of claim 1, characterized in that the gap (6) is formed between the top side (513) of a circular ring shaped central portion (51) of the carrier section (5) and the bottom side (415) of the hub (41) of the impeller wheel (4).
 20. The electric drive unit of claim 1, characterized in that all cooling surfaces (71) of the cooling body (7) reach into the hub inner space (414).
 21. The electric drive unit of claim 1, characterized in that the inner wall (413) of the hub (41) of the impeller wheel (4) is connected with the electric motor (3), and in that wings (42) are secured to the outer wall (411) of the hub (41) of the impeller wheel (4).
 22. The electric drive unit of claim 1, characterized in that the hub inner space (414) is divided into individual hub chambers (45) by ribs (44) interconnecting the outer wall (411) with the inner wall (413).
 23. The electric drive unit of claim 22, characterized in that the cooling surfaces (71) of the cooling body (7) reach into the hub inner space (414) up to the ribs (44).
 24. The electric drive unit of claim 1, characterized in that the stator (31) comprises a plurality of stator coils (35) formed as circle segments, and in that the stator (31) has a circular configuration with a central hole (38) for receiving the rotational axis (39) of the electric motor (3).
 25. The electric drive unit of claim 1, characterized in that a stamped grid (24) is provided for electrically contacting the structural components (21) of the electronic control module (2), said stamped grid (24) being connected with the bottom side (332) of the motor carrier (33), and wherein connector elements (28) in the form of stamped grid tabs (26) lead from the stamped grid to the connector contacts (36, 37) of the electric motor (3).
 26. The electric drive unit of claim 1, characterized in that electronic control unit (2) comprises commutating switches for commutating the electric motor (3).
 27. The electric drive unit of claim 26, characterized in that the commutating switches are constructed as commutation transistors (21).
 28. The electric drive unit of claim 1, characterized in that the electric motor (3) is constructed as a brushless DC-motor
 29. The electric drive unit of claim 1, characterized in that the electric motor (3) is constructed as an outer rotor motor comprising a rotor (32) rotating on the outer side of the stator (31). 